by Justice Thu May 13, 2010 7:39 pm
solution:
cos(x+y)= cosxcosy-sinxsiny
cos(sin^-1x + cos^-1 x)
Let sin^-1x = u
Let cos^-1 x= v
cos( u + v) = cos u cos v - sin u sin v = cos(sin ^-1x) cos (cos-1x) - sin( sin^-1x) sin (cos -1x)
ok so... we know sin(sin-x) and cos(-x) are both equal to x and cos(sin ^-1x)= sin (cos -1x)
so we can assume x-x=0
Last edited by lev_93 on Thu May 13, 2010 7:53 pm; edited 1 time in total